1. Field of the Invention
This invention relates to a coupling for connecting fire fighting hoses or the like or for connecting a hose and a pump or some other apparatus and to a method of manufacturing such a coupling. More particularly, the present invention relates to a coupling comprising a pair of coupling main bodies that are structurally identical and not discriminable as male and female and to a method of manufacturing such a coupling.
2. Description of the Related Art
Plug-in type couplings for connecting hoses including fire fighting hose are known. A plug-in type coupling of the type under consideration typically comprises a pair of coupling main bodies that are to be brought into axial engagement with each other to connect hoses. Such a plug-in type coupling is defined by Japanese Industrial Standards JIS B 9911 and referred to "Machino-shiki coupling", which is currently very popular.
Such a plug-in type coupling can connect and release hoses with simple operation and hence is advantageously used as a coupling for connecting fire fighting hoses that requires an enhanced level of fast and reliable operability.
However, such a known plug-in type coupling comprises a pair of coupling main bodies that are discriminable as male and female. In other words, a plug-in type coupling is comprised of a male metal fitting and a female metal fitting and two male or female metal fittings cannot be brought into engagement if they are put together. Thus, there arises a problem when fire breaks out and fire fighting hoses have to be connected for extension that male or female metal fittings are put together for hose connection by mistake. This is a problem that should preferably be totally eliminated for fast and reliable fire fighting operations. Additionally, such a known plug-in type coupling is costly because two structurally different metal fittings, a male metal fitting and a female metal fitting, have to be manufactured for it.